Scheduled Tasks & Background Agents allows apps to run in background in Windows Phone while the app is not running in foreground. There are two types of Scheduled Tasks referenced called Periodic Tasks & ResourceIntensive Tasks which helps to implement background agent scaling.

Periodic Tasks: Periodic agents run for a small amount of time on a regular recurring interval. Typical scenarios for this type of task include uploading the device’s location and performing small amounts of data synchronization.

Resource-Intensive Tasks: This tasks works for long period of time when the phone meets a set of requirements relating to processor activity, power source, and network connection. A typical scenario for this type of task is synchronizing large amounts of data to the phone while it is not being actively used by the user.

The Background Agent LifeCycle for Windows Phone: The app can have at least of one type of Scheduled tasks either Periodic Tasks or Scheduled Tasks or even both. So the schedule on which the agent runs depends on which type of task it is registered as.

There are some constraints features on both of Periodic Tasks & Resource-Intensive Tasks . For details Click here.

Implement Background Tasks for Windows Phone 7.1 Mango : In order to implement it you need to a Windows Phone application project in VS 2010 SP1 from Silverlight for Windows Phone template.